Question

(a) Describe Thomson's model of the atom. Which subatomic particle was not present in Thomson's model of the atom?

Answer 1

(a) Thomson proposed a model of an atom that is similar to a Christmas pudding.
The electrons, in a sphere of positive charge, are like currants (dry fruits) in a spherical Christmas pudding. We can also compare an atom to a watermelon. The positive charge in the atom is spread all over like the red edible part of the watermelon, while the electrons are studded in the positively charged sphere like the seeds in the watermelon.

Thomson proposed that:
  (i) An atom consists of a positively charged sphere and the electrons are embedded in it.
  (ii) The negative and positive charges are equal in magnitude. So, the atom as a whole is electrically neutral.

This model did not tell us about the presence of neutrons in the atom.
Although Thomson’s model explained that atoms are electrically neutral, the results of experiments carried out by other scientists could not be explained by this model, as we will see below.

Neutron was not considered in Thomson's model of the atom.